The invention relates to a projector-type headlamp for a vehicle, and more particularly to a low-beam headlamp.
In recent years, projector-type headlamps have come to be frequently adopted as headlamps for vehicles.
As shown in FIG. 1, a projector-type headlamp comprises a light source 102 disposed on an optical axis Ax of the headlamp which extends in the longitudinal direction of a vehicle, a reflector 104 for reflecting light from this light source 102 in a forward direction close to the optical axis Ax, and a focusing lens 106 disposed forwardly of the reflector 104.
Further, for using this projector-type headlamp as a low-beam headlamp, a light shielding plate 108 is provided between the focusing lens 106 and the reflector 104. The shielding plate 108 eliminates upwardly illuminating light by shielding part of the reflected light from the reflector 104. As a result, a luminous intensity distribution pattern P is formed for low beam light, showing a light-dark borderline CL, as shown in FIG. 2.
Since the upwardly illuminating light of such a projector-type headlamp is eliminated almost completely by the light shielding plate 108, an overhead sign installed above the road surface ahead of the vehicle cannot often be seen clearly.
Accordingly, an approach has been adopted, as shown in FIG. 3, to attach in the vicinity of an upper edge 108a an L-shaped plate 110 extending diagonally downward from a front surface 108b of the light shielding plate 108. Reflected light from the reflector 104 is deflected or reflected upward by an upper inclined surface 110a of the L-shaped plate 110. The reflected upward light propagates from the focusing lens 106 to illuminate overhead signs.
However, with the projector-type headlamp, a focal position of the focusing lens 106 is generally set at the upper edge 108a of the light shielding plate 108. The L-shaped plate 110 is attached to the front surface 108b of the light shielding plate 108 near the upper edge. Therefore, when the headlamp is viewed from a forward and slightly upper direction, the L-shaped plate 110 is seen enlarged by the lens action of the focusing lens 106, as shown in FIG. 4. External light causes the upper inclined surface 110a of the L-shaped plate 110 to be seen as brightly lit, while a front-end surface 110b of the L-shaped plate 110 remains dark. Hence, the visual appearance of the headlamp is degraded when exposed to external light.
The invention of this application has been devised in view of the above-described circumstances. The object is to provide a projector-type headlamp for a vehicle capable of obtaining light for illuminating overhead-signs without impairing the appearance of the headlamp.
In embodiments of the invention, the above object is attained by providing a structure for illuminating overhead signs.
An embodiment of the invention provides a projector-type headlamp for a vehicle comprising: a light source disposed on an optical axis of the headlamp extending in a longitudinal direction of a vehicle; a reflector for reflecting light from the light source in a forward direction close to the optical axis; a focusing lens disposed forwardly of the reflector; and a light shielding plate interposed between the focusing lens and the reflector so as to eliminate upward illuminating light by shielding part of the reflected light from the reflector, wherein a projection, which has an upper inclined surface extending diagonally downward in a forward direction and is adapted to deflect or reflect reflected light from the reflector upwardly at the upper inclined surface, is integrally formed at a front surface of the light shielding plate and at a position in a vicinity of a upper edge thereof, and a front-end portion of the projection is formed with a curved surface in such a manner as to be smoothly connected to the upper inclined surface.
The phrase xe2x80x9cdeflect or reflect . . . upwardlyxe2x80x9d means to deflect or reflect the reflected light from the reflector incident upon the upper inclined surface of the projection such that an angle of downward inclination of the reflected light becomes small, but does not necessarily mean to reflect the light upward.
As long as the aforementioned xe2x80x9cprojectionxe2x80x9d is capable of deflecting or reflecting the reflected light from the reflector in an upwardly direction and capable of allowing the light for illuminating overhead-signs to propagate from the focusing lens, an arrangement of the upper inclined surface, including its planar shape, size, the angle of downward inclination and the like, should not be limiting.
The projector-type headlamp in accordance with an embodiment of the invention is arranged such that a projection having an upper inclined surface extending diagonally downward in a forward direction is integrally formed at a front surface of the light shielding plate and in the vicinity of an upper edge of the plate, and the reflected light from the reflector is deflected or reflected upwardly from the upper inclined surface. Accordingly, light for illuminating overhead-signs can propagate from the focusing lens.
When the headlamp is observed from a forward and slightly upper direction, the projection is seen enlarged by the lens action of the focusing lens. However, when the headlamp is exposed to external light, since the front-end portion is formed with a curved surface and smoothly connected to the upper inclined surface, the front-end portion does not appear as dark relative to the upper inclined surface which is seen as brightly lit by the external light. The front-end portion can be seen as being lit with the brightness changing gradually. Moreover, since the projection is formed integrally with the light shielding plate, its front-end portion can be easily formed with a curved surface. Further, compared to the L-shaped plate attached to the light shielding plate in a conventional manner, the projection""s portion connected to the general portion of the light shielding plate can be seen as integrated and uniform in terms of its external appearance.
Therefore, it is possible to provide a projector-type headlamp for a vehicle capable of generating light for illuminating overhead-signs without impairing the appearance of the headlamp.
In addition, the portion of the light shielding plate in the vicinity of its upper edge is expected to reach a high temperature since the reflected light from the reflecting surface of the reflector is concentrated there. Also, the temperature of the projection is expected to become high. However, since the projection is formed integrally with the light shielding plate, the projection is unlikely to undergo thermal deformation, and the heat from the light shielding plate can be efficiently dissipated through the projection.
Further, although the angle of downward inclination of the upper inclined surface is not limiting as described above, if the angle of downward inclination is set to 25 to 35xc2x0, the illuminating light can propagate from the focusing lens at an angle of upward inclination suitable for illuminating the overhead signs. The reason for the 25xc2x0 lower-limit is that if it is set to less than 25xc2x0, the light from the upper inclined surface and a; through the focusing lens may be directed upward to a region above the overhead sign. On the other hand, the reason for the 35xc2x0 upper-limit is that if it is set to more 35xc2x0, the light from the upper inclined surface and through the focusing lens may be directed downward to a region below the overhead sign.
The aforementioned xe2x80x9cupper inclined surfacexe2x80x9d may be one whose rear-end portion extends up to the front surface of the light shielding plate or one whose rear-end portion extends halfway. Whichever case, the line of intersection between the upper inclined surface or its rearwardly extending surface and the front surface of the light shielding plate is preferably set at a position 0.5 to 3.0 mm below the upper edge of the light shielding plate. The reason for this is that if the distance is less than 0.5 mm, the intensity of light incident upon the upper inclined surface can become substantially high, and upwardly illuminating light may exceed a luminosity necessary for illuminating the overhead sign and may cause glare. On the other hand, if the distance exceeds 3.0 mm, the intensity of light incident upon the upper inclined surface can become insufficient. It can also be difficult to obtain a luminosity necessary for illuminating the overhead sign. Therefore, it is preferable to set the distance in the range of 0.5 to 3.0 mm.
Instead of using one projection, a plurality of projections can be juxtaposed transversely to obtain light suitable for illuminating overhead signs. Each projection""s arrangement, its size of the upper inclined surfaces, its downward angle or the like may be appropriately set.